The field of the disclosure relates generally to centrifugal pump assemblies, and more specifically, to centrifugal pump assemblies that include an axial flux electric motor coupled to an impeller.
At least some known centrifugal pumps include an impeller for channeling a fluid through the pump. The impeller is coupled to a shaft via a hydrostatic bearing, which is coupled to a rotor of an electric motor such that rotation of the rotor causes rotation of the bearing and the impeller. In at least some known electric motors, a separate pump is used to deliver a pressurized fluid flow required for operation of the hydrostatic bearing. An additional pump increases both the complexity and cost of the pump system, which may inhibit the use of hydrostatic bearings in cost sensitive applications.
Furthermore, at least some known centrifugal pumps include hydrodynamic bearings. When designing a hydrodynamic bearing there are a number of factors to consider. One of them is the ability of the bearing to hydro dynamically ‘lift’ in operation and separate the rotating bearing component from the stationary bearing component. It is critical the bearing ‘lifts’ to ensure correct operation. If the bearing does not ‘lift’ there will be large friction between the two bearing materials causing large friction torque resistance, drag torque resistance and material ware. To ensure bearing lift, the bearing is designed to have a pressure velocity (PV) factor to fall within a predetermined range. The PV factor is based on the velocity of the rotating component and the coefficient of friction between the rotating bearing component and the stationary bearing component. However, at least some known rotating bearing components are flat disks, leading to a velocity differential between the inner diameter and the outer diameter of the disk. This velocity differential leads to a wide range of PV factors, at least some of which may be outside the desired range. Operational of the hydrodynamic bearing outside the desired PV factor range may lead to inefficient operation of the pump assembly and/or to a shortened service lifetime of the bearing components.